The present invention relates to the field of tuning systems for television receivers and the like which include a memory for storing binary signals representing tuning information.
Recently, electronic tuning systems have been proposed for television receivers which include a memory for storing binary signals representing tuning voltages for controlling an associated voltage controlled local oscillator in order to tune various channels a viewer may select. Although these memory type of tuning systems tend to be more versatile and less expensive than other types of electronic tuning systems such as, for example, those employing frequency synthesizers, they suffer the disadvantage that at least some programming by the manufacturer, and in some instances by the individual viewer, is required to enter tuning information into the memory.
In some of the proposed memory type tuning systems the size of the memory, i.e., the number of locations in which information can be stored, is limited to reduce the cost of the tuning system. As a result, in these tuning systems only the tuning information for a limited number of preferred channels less than the total number of channels allocated to the television band can be stored. Since the channels preferred by a particular viewer, either because of program content or because of the reception conditions at the viewer's location, are known only to a viewer, for those memory type tuning systems including a memory with only a limited number of memory locations, programming is to be accomplished by the viewer himself. Programming a memory type tuning system involves not only the selection of the preferred channels, but also involves the generation of binary signals representing tuning voltages and channel number display information corresponding to the preferred channels. For viewers who are used to the conventional type of mechanical tuning systems including a mechanical rotary channel selector switch, the programming procedures for a memory type tuning system may present considerable difficulty and lead to unnecessary costly and annoying service calls. Therefore, it is desirable that memory type tuning systems be arranged to simplify as much as possible the required programming procedures.
One of the problems encountered in programming a memory type tuning system is that of correlating a viewable picture to a channel number. That is, as the tuning voltage is adjusted until a viewable picture is produced, unless a station identification interval is fortuitously transmitted while the viewable display is present or the viewer happens to know on what channel the program being displayed is being transmitted, the viewer has no way of knowing the channel to which the receiver is presently tuned and cannot program the corresponding channel number display information.
To overcome this problem, it is possible to provide an electromechanical voltage meter which is responsive to the analog tuning voltage so as to provide a viewer with an indication of the relative tuning position (see, for example, the tuning system disclosed in the "Magnavox Service Manual--703777 Videomatic Touch Tune Assembly," Manual No. 7353, File Volume 12, published by the Magnavox Company, Fort Wayne, Ind.). Not only do electromechanical meters tend to be relatively expensive and, because of their bulk, tend to detract from the appearance of the receiver, but they may be difficult to read by viewers not familiar with electronic equipment. Moreover, electromechanical meters may not provide sufficient resolution between tuning positions where the preferred channels are closely spaced. That is, for example, a viewer may not be able to distinguish between channels 4, 5 or 6.
It is also possible to provide an on-screen display system which provides an on-screen display showing a scale calibrated in channel numbers (rather than in tuning voltages) and a bar which changes length along the scale as a tuning voltage is adjusted (see, for example, the display disclosed in the "General Instrument AY-3-8330--Electronic On-Screen TV Tuning Scale" data sheet available from General Instrument). While such an on-screen display may overcome some of the disadvantages of an electromechanical meter, it may nevertheless be difficult for a viewer to utilize because it provides information in the same analog format as does an electromechanical meter. In addition, on-screen display systems tend to add expense to the cost of the tuning system and therefore may not be provided.
Thus, it is desirable that a memory type tuning system include an arrangement for providing an indication of tuning voltages in a format with which ordinary viewers are relatively familiar and which desirably include provisions which tend to minimize the possibility of confusion on the part of a viewer.